掺加铬对硼硅酸盐玻璃固化体结构影响

动力堆乏燃料经后处理产生的高放废液中铬的含量比生产堆略高,为了尽可能提高玻璃固化体对有毒有害的重金属铬废物的包容能力,减少该类废物玻璃固化后最终废物体积,实验通过掺加不同量的氧化铬研究其对于硼硅酸盐玻璃(摩尔比n(SiO_2)∶n(B_2O_3)∶n(Na_2O)∶n(Li_2O)=1.03∶0.32∶0.18∶0.18)包容模拟动力堆高放废液的量及玻璃样品结构的影响。六种玻璃样品的X射线衍射和拉曼光谱分析结果显示,废物包容量从10%增至20%(质量分数),硼硅酸盐玻璃样品的结构明显提高(Q1比例降低,Q2等比例提高)。废物包容量增至20%(质量分数)情况下,铬的掺杂量可以达到0.5%(质量分数),玻璃样品没有出现结晶相,其结构比不掺加铬的样品更加稳定。同时,向废物包容量为20%(质量分数)的玻璃样品增加铬的掺杂量增至1%(质量分数),由于铬含量超出硼硅酸盐玻璃包容铬的限值而溢出,形成氧化铬晶相,降低了玻璃样品结构的稳定性和对废物包容的能力。PCT测试结果和SEM分析结果同Raman和XRD分析结果一致。     

钼酸盐在硼硅酸盐玻璃体系中的溶解

在英国和法国的很多高放核废料中都含有大量的钼。钼在核废料玻璃中的溶解度很低,过量的钼会导致玻璃产生钼酸盐分相从而影响核废料玻璃化的效率和安全。主要研究了钼酸盐在硼酸盐玻璃中的溶解度与玻璃中碱土金属元素的关系以及钼酸盐的溶解对玻璃的结构和性质的影响。在其它玻璃组分不变的情况下,对玻璃中的碱土金属(由镁至钡)进行等摩尔量替换。结果发现,当碱土金属为钙时钼酸盐的溶解度最高,为2.84 mol%。XRD结果显示除了明显分相的玻璃外其它均一玻璃均为无定形态。SEM结果显示玻璃基体内的分相大多为球状/水滴状并呈随机分布;其尺寸与钼酸盐的过量程度有关,但直径都小于1?m。对钙硼硅酸盐玻璃中析出相的EDX分析表明其中富含钼和钙,而TEM结果证明这些析出相为晶体相且符合钼酸钙的电子衍射特征。含钼玻璃有两个强烈的拉曼峰(分别位于320和910 cm–1附近):其强度随玻璃中钼含量的增加而增加,其位置随玻璃中碱土金属元素的变化而偏移。此外,钼的加入也会导致玻璃的玻璃转变温度降低以及玻璃密度增加。     

钠硼硅酸盐玻璃分相过程的NMR研究

利用²⁹Si、¹¹B、²³Na MAS NMR,研究了一定组成的Na₂O－B₂O₃－SiO₂玻璃在不同温度下其微结构随分相处理时间的变化．结果表明,随分相过程的进行,[SiO₄]结构单元的非桥氧之间逐渐脱氧,聚集程度逐渐提高,富硅相中的[BO₃]结构与氧结合转变为[BO₄]结构并进入富钠硼相,两相成分差逐渐增大,分相是扩散传质的结果．在较高的分相温度下,玻璃结构调整较快,因而更早地接近分相的平衡态．     

氧化硼对硅酸盐玻璃固化体结构及抗浸出性能的影响

以SiO2、Al2O3、B2O3、CaO、Na2O为原料,加入5%CeO2(质量分数)作为模拟核素,利用熔融法制备硼硅酸盐玻璃固化体,对含锕系元素的放射性废物进行固化处置。通过傅里叶红外光谱仪、紫外激光拉曼光谱仪和差热分析仪等对热处理后玻璃固化体进行表征,以电感耦合等离子体质谱测试玻璃固化体抗浸出性能。结果表明:B2O3含量为15.79wt%时固化体玻璃化转变温度Tg最大;玻璃中存在[SiO4]、[BO3]、[BO4]等基团,随着B2O3含量的增大,部分[BO4]转变为[BO3];Ce在产品一致性测试法(PCT)下标准化浸出率NR先减小后增大,B2O3含量达到15.79wt%时玻璃抗浸出效果最好。     

硼硅酸盐玻璃的低温烧结研究

莫来石陶瓷材料作为高性能集成电路的候选材料,在电子封装基片领域有着广阔的应用前景,但过高的烧结温度限制了其发展。本文利用溶胶-凝胶法制备能够在低温实现烧结的硼硅酸盐玻璃,作为引入相以实现莫来石陶瓷封装材料的低温共烧,通过研究CaO、B2O3、SiO2的不同组成并引入ZnO、P2O5作为助烧剂,最终制得了能够在800℃实现低温烧结的硼硅酸盐玻璃,其线性收缩率约为22.4%~24.0%,表观密度为2.21±0.1,ε=4.1±0.2,tgδ<0.06%,Rj>1.0×1012Ω.cm。     

铽铝硼硅酸盐磁光玻璃形成性能及热稳定性研究

采用Zhou W C提出的玻璃形成区研究方法探索了铽硼硅酸盐磁光玻璃形成区域范围,采用魔角核磁共振谱仪(MAS NMR)和示差扫描量热仪(DSC)对玻璃结构和特征温度能进行了表征,研究了Tb2O3和Al2O3对玻璃形成能力和玻璃结构的影响,同时引入玻璃析晶参数β讨论玻璃热稳定性.结果表明:Tb2O3的掺入量受玻璃形成区域的限制,在Tb2O3含量为30%(摩尔分数)时以及Al2O3含量为25%(摩尔分数)时玻璃形成能力较强;铽铝硼硅酸盐玻璃结构中硼氧多面体和铝氧多面体主要以四配位的[BO4]和[AlO4]形式存在,仍存在少量三配位的[BO3]和五配位的[AlO5];Tb2O3含量为30%(摩尔分数)的玻璃β值较大,热稳定性能较好.     

网络修饰体对铕-镝共掺铝硼硅酸盐玻璃白光发光影响

采用高温熔融的方法,在空气中制备了一系列添加不同网络修饰体氧化物的Eu2 O3和Dy2 O3共掺杂铝硼硅酸盐玻璃,并测试了其在紫外光激发下的发光性能.从发射谱中可以看到归属于Eu2+、Eu3+和Dy3+离子能级跃迁的蓝、绿、黄、红等多色发射带共存.这些发射带之间的相对强度会随着网络修饰体氧化物的改变而变化,从而导致发光色度的变化.加入适当的网络修饰体氧化物可得到合适的白光发射.此外,在空气中制备过程中发生了Eu3+→Eu3+的还原反应.用Li2O取代ZnO时,该还原反应程度降低,而用CaO取代BaO时该还原反应程度增强,其机制与玻璃组分的光碱度有关.     

硼硅酸盐生物活性玻璃多孔支架的制备

Na2O-CaO-SiO2-P2O5-B2O3系硼硅酸盐生物玻璃是一类具有良好生物活性和降解性能的组织工程材料.本研究中,采用有机泡沫浸渍法,乙醇作溶剂,乙基纤维素作添加剂,将硼硅酸盐玻璃粉体制备成具有三维连通网状结构的组织工程多孔支架.通过调节浆料的固相含量和乙基纤维素含量,改善坯体的涂覆量,在支架孔径为300～500um,孔隙率高于80%时,使支架抗压强度从0.03MPa提高到0.36MPa.根据蜂窝状结构模型分析,发现采用高强度玻璃,优化浆料是改善多孔材料结构和力学性能的有效途径.用该模型理论指导,由Na2O-CaO-SiO2-P2O5-B2O3系统制成的另一种硼硅酸盐玻璃支架,其抗压强度可达5～8MPa.实验表明有机泡沫浸渍法在制备组织工程支架中有广泛的应用前景.     

低介电高硼硅酸盐玻璃的性能研究

以硼硅酸盐玻璃为基础玻璃系统,研究了超高硼含量区间,硼硅酸盐玻璃结构和性能的变化规律。通过红外光谱分析了硼硅酸盐玻璃在不同B2O3含量的情况下的结构变化,测试了玻璃的热膨胀系数、转变温度、软化温度和高温粘度。研究结果表明,高硼玻璃难以析晶;随着B2O3含量的增加,玻璃结构中[BO4]、[BO3]数量增多,其中以[BO3]为主;玻璃的热膨胀系数呈现出S型变化,转变温度和软化温度都逐渐减小;介电常数与介电损耗都出现极小值,过量的B2O3会起到反作用;此外B2O3起到降低高温粘度的作用,但降低作用有限。     

低铝高硼硅玻璃基本形成过程及性能研究

采用热重-微分热重-差示扫描量热(TG-DTA-DSC)同步热分析方法,对低铝高硼硅玻璃(ABS)熔制过程中发生的理化反应进行研究。作为比较,对普通钠钙硅玻璃(NCS)的性能做了相应的研究。通过粘度测试分析发现,所制备的低铝高硼硅玻璃软化点接近800℃,具有极好的耐热性。其工作温度和熔化温度较NCS均有大幅提高,分别为1375～1160℃和1699℃。热膨胀曲线表明所制备的ABS具有非常低的热膨胀系数,α(20～300℃)=3.9×10-6K-1,具有优良的抗热震性。     

Adsorption reactions of carboxylic acid functional groups on sodium aluminoborosilicate glass fiber surfaces

Multicomponent silicate glasses are ubiquitous in modern society as evidenced by their inclusion in applications ranging from building materials and microelectronics to biomedical implants. Of particular interest in this study is the interface between multicomponent silicate glasses and adhesive polymers. These polymeric systems often possess a variety of different organic functional groups. In this study, we selected acetic acid as a probe molecule representative of the carboxylic acid functional group found in many adhesives. We have used Fourier transform infrared spectroscopy (FT-IR) and NMR to study the interaction of acetic acid with the surface of sodium aluminoborosilicate continuous glass fibers. Methods were developed that enable analyses to be carried out without damaging or altering the pristine as drawn fiber surface. While dosing the surface of fumed silica with acetic acid resulted in the formation of silyl ester groups, analogous dosing of sodium aluminoborosilicate glass fibers resulted in the formation of carboxylate species, principally coordinated to sodium, while silyl ester groups were not observed.     

Dissolution and geopolymerization of synthetic fly ash glass

Journal of Materials Science - Two fly ash glasses were synthesized and dissolved in KOH at a water/solid ratio of?≤?0.3. We measured reaction kinetics, gel formation, and...     

Dissolution mechanisms of boro-silicate glass fibres in saline solution with added dissolved silica

Experiments of dissolution of a soluble boro-silica glass were performed at 37°C in a saline solution without and with 50, 75 and 100 ppm of added silica. After reaction silica concentration was measured by AAS and colorimetry and fibers were investigated by SEM-EDS and XPS. The results give informations on the dissolution velocity of the glass and the factors controlling the formation rate of the gel layer and its composition. The dissolution velocity measured at the unaltered glass-gel interface is not significantly decreased by the silica concentration in solution whatever its origin (leaching of the glass fibres or initial addition). Accordingly, gel formation is controlled by the chemical reactions rate at, or near, the boundary of the unaltered core. The composition and the stucture of the gel layer are depending on the silica concentration in solution above a threshold of about 50 ppm. The framework of the gel appears to play the more important role in the dissolution velocity of the glass.     

Dissolution process of surface oxide film during diffusion bonding of metals

Two models of the dissolution process of surface oxide film in metals (copper and titanium) are described in order to estimate the dissolution time t _s required for the oxide film to dissolve in the metals completely. One is based on impurity diffusion (model 1). The other is given by reaction diffusion (model 2). Model 1 was applied to estimate t _s in copper and -titanium but model 2 for t _s of -titanium because of the formation of -phase. In these models, the dissolution process is assumed to be controlled by the oxygen diffusion in metals. Bonding tests were performed in order to verify the calculated results. The experimental results suggest that model 1 is valid in Cu-Cu bonding. Also, as for -titanium, no retardation of the bonding process was observed. This was in agreement with model 2. However, for -titanium below 1000 K, the retardation time was much longer than the dissolution time calculated by model 1, i.e. the retardation below 1000 K cannot be dictated by the diffusion-controlled process. A new model is therefore proposed. The dissociation rate of the oxide film is taken into account in the new model. This new model can explain the retardation of the bonding process.     

Reduction of Eu to Eu in aluminoborosilicate glasses under ionizing radiation

Eu₂O₃-doped aluminoborosilicate glasses were prepared by melting in air at high temperature (∼1500 °C). It was shown by luminescence and Electron Paramagnetic Resonance (EPR) measurements that both Eu³⁺ and Eu²⁺ ions can exist simultaneously in the glass matrix studied after glass synthesis as well as after exposure to ionizing radiation. Increase of total Eu₂O₃ concentration leads to the increase of Eu³⁺ luminescence intensity while the luminescence intensity of Eu²⁺ ions tends to decrease. In contrast the EPR indicates that the amount of Eu²⁺ ions in the glass increases with total Eu₂O₃ concentration. The difference in the results of the two spectroscopies is explained in terms of energy transfer from Eu²⁺ to Eu³⁺ leading to an Eu²⁺ luminescence quenching. Irradiation results in the increase of reduced Eu²⁺ quantity detected by EPR measurements. It was shown that Eu²⁺ ions are located in both high (g ∼ 4.6) and low symmetry (“U’ spectrum) sites in the structure of aluminoborosilicate glasses. The increase of Eu²⁺ content by the increase of the irradiation dose manifests the strong reduction process Eu³⁺ → Eu²⁺.     

Preparation of cordierite glass by the sol-gel process

Cordierite glass was prepared by the sol-gel process from magnesium, Al(OC₄H₉)₃ and Si(OC₂H₅)₄. The solution having cordierite-like structure was formed by refluxing the raw materials, followed by gelling and drying to 150° C in the saturated water vapour to hydrolyse completely. On heating the gel, AlO₆ groups transformed into AlO₄ groups, in which aluminium ions were incorporated in SiO₄ tetrahedra units to form a Si-O-Al network structure. The gel was converted into the transparent dense glass by heating above 850° C. The glass transition temperature, 820° C, thermal expansion coefficient, 3.1×10^–6° C^–1, Vickers hardness, 6.22 GPa and density, 2.59 g cm^–3 were almost the same as those of the conventional glass.     

Positron lifetime study of the devitrification process in a cordierite glass

The devitrification of the 13.3% MgO-32.0% Al₂O₃-52.7% SiO₂-2.0% BaO ceramic-glass via isochronal heating up to a stable crystalline structure has been studied by the positron annihilation technique. The lifetime spectra showed two components. This devitrification results as a two-stage process. The long-lifetime ₂, attributed to the pick-off annihilation ofortho-Ps states, decreased on crystallization, but it was insensitive to the hexagonal-orthorhombic transformation of the crystalline cordierite. On the contrary, the effective lifetime of positrons annihilating in states that are not Ps, increased. This increase has been attributed to the Al/Si order process inherent to the hexagonal-orthorhombic transformation. Moreover, the Ps fraction in the crystalline phases was higher than in the glassy phase. However the free volume model might qualitatively explain the relationship observed betweenI ₂ and ₂.     

Double-ion-exchange process in glass for the fabrication of computer-generated waveguide holograms

We experimentally optimize double-ion-exchange process parameters to achieve a designed phase modulation for a wave front passing through a computer-generated waveguide hologram and numerically analyze the effects of fabrication errors. We also demonstrate a gradient-thickness waveguide hologram for ? beam splitting.